1. Field of the Invention
This invention relates to a process for the manufacture of ethanol by reaction of carbon monoxide with hydrogen in the presence of a novel catalyst composition.
2. Description of the Prior Art
Oxygen-containing compounds having two carbon atoms such as ethanol and acetaldehyde have hitherto been manufactured according to petrochemical processes using naphtha as a raw material. However, the recent sharp rise in crude oil price has caused a significant increase in the production cost of these carbon compounds and it has become necessary to employ a different raw material.
In this connection, investigations were carried out in various processes for the manufacture of oxygen-containing compounds having two carbon atoms from a mixed gas comprising carbon monoxide and hydrogen, both of which are available abundantly and inexpensively.
As a result, various processes became known wherein a mixed gas comprising carbon monoxide and hydrogen is subjected to reaction in the presence of a catalyst containing rhodium as an essential component and further containing metals such as manganese, titanium, zirconium and iron or their oxides to selectively manufacture oxygen-containing compounds having two carbon atoms, (e.g., GB Patent Nos. 1,501,891, 1,501,892 and 1,549,437; U.S. Pat. Nos. 4.463,105; etc.)
In these processes, however, hydrocarbons such as methane are generated in large amounts as by-products and the selectively of the oxygen-containing compounds is low or, when the selectively of the oxygen-containing compounds is high, the yield of these compounds is very low. Further, the yield of desired compounds per unit amount of rhodium, which is an expensive noble metal, is low. Therefore, these processes are not satisfactory from either the economical or the technical standpoint.
Various processes additionally using modified catalysts have been proposed in order to manufacture oxygen-containing compounds having two carbon atoms in high yield and with high selectivity. For instance, manganese, lithium, etc. were used as a co-catalyst in CA Patent No. 1,146,592 and Japanese Patent Public Disclosure (Laid-Open Publication) No. 8334/1981; lithium, magnesium and vanadium were used in Japanese Patent Public Disclosure (Laid-Open Publication) Nos. 62231/1982 and 109734/1982; scandium, yttrium and ytterbium were used in Japanese Patent Public Disclosure (Laid-Open Publication) No. 62233/1982; magnesium was used in U.S. Pat. No. 4,224,236; vanadium was used in Japanese Patent Public Disclosure (Laid-Open Publication) No. 62232/1982; and chromium was used in U.S. Pat. No. 4,327,190. In all of these processes, acetaldehyde and acetic acid are manufactured as main products, and the selectivity of ethanol is low.
Further, alcohol mixtures are produced by contacting synthesis gas with a catalyst containing copper, titanium, and at least one selected from the group consisting of chrome, manganese, cobalt, molybdenum, rhodium, platinum and iron, and an alkali or alkaline earth metal, (U.S. Pat. No. 4,459,369), or with an oxide complex catalyst containing copper, thorium, an alkali metal, etc., (U.S. Pat. No. 4,298,354), or with a catalyst comprising an iron group metal and rhodium, etc., (U.S. Pat. No. 4,537,909). In all of these processes, the selectivity of ethanol is also low.
Thus, no process has yet been made available which is capable of efficiently and economically manufacturing ethanol from a gas comprising carbon monoxide and hydrogen.